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US20020193041A1 - Method of manufacturing a dispenser cathode for a cathode ray tube - Google Patents

Method of manufacturing a dispenser cathode for a cathode ray tube Download PDF

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Publication number
US20020193041A1
US20020193041A1 US10/135,338 US13533802A US2002193041A1 US 20020193041 A1 US20020193041 A1 US 20020193041A1 US 13533802 A US13533802 A US 13533802A US 2002193041 A1 US2002193041 A1 US 2002193041A1
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US
United States
Prior art keywords
metal
cathode
group
oxide
ray tube
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Abandoned
Application number
US10/135,338
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English (en)
Inventor
Georg Gaertner
Christopher Goodhand
Simon Hodgson
Andrew Baker
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Koninklijke Philips NV
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
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Assigned to KONINKLIJKE PHILIPS ELECTRONICS N.V. reassignment KONINKLIJKE PHILIPS ELECTRONICS N.V. ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: BAKER, ANDREW PETER, HODGSON, SIMON NICHOLAS, GOODHAND, CHRISTOPHER JAMES, GAERTNER, GEORG FRIEDRICH
Publication of US20020193041A1 publication Critical patent/US20020193041A1/en
Abandoned legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J9/00—Apparatus or processes specially adapted for the manufacture, installation, removal, maintenance of electric discharge tubes, discharge lamps, or parts thereof; Recovery of material from discharge tubes or lamps
    • H01J9/02—Manufacture of electrodes or electrode systems
    • H01J9/04—Manufacture of electrodes or electrode systems of thermionic cathodes
    • H01J9/042—Manufacture, activation of the emissive part
    • H01J9/047—Cathodes having impregnated bodies

Definitions

  • the invention relates to a method of manufacturing a dispenser cathode for a cathode ray tube which comprises a cathode carrier with a cathode base and a porous metal matrix body which is infiltrated with an electron-emitting material.
  • the functional groups of a cathode ray tube include an electron-emitting cathode which generates the electron flow in the cathode ray tube.
  • An electron-emitting cathode for a cathode ray tube is usually a heatable dispenser cathode with an electron-emitting, oxide-containing cathode body.
  • a dispenser cathode When a dispenser cathode is heated, electrons are vaporized from the electron-emitting coating into the surrounding vacuum.
  • the quantity of electrons which can be emitted from the cathode coating depends on the work function of the electron-emitting material.
  • Nickel which is normally used as a cathode base, itself has a relatively high work function. Therefore the cathode base for a dispenser cathode is also fitted with a metal matrix body infiltrated with an electron-emitting material. Its main task is to improve the electron-emitting properties of the cathode base.
  • One characteristic of the electron-emitting materials of dispenser cathodes is that they contain an alkaline earth metal in the form of an alkaline earth metal oxide.
  • a correspondingly formed metal matrix body is coated for example with the carbonates of the alkaline earth metals in a binding agent preparation.
  • the carbonates are converted into the alkaline earth metal oxides at temperatures of around 1000° C.
  • the cathode already emits a perceptible emission stream but this however is not yet stable.
  • An activation process follows. This activation process converts the originally non-conductive ion lattice of the alkaline earth oxides into an electronic semi-conductor as donor-type impurities are integrated into the crystal lattice of the oxides.
  • the impurities essentially consist of elementary alkaline earth metal e.g. calcium, strontium or barium.
  • the electron emission of such dispenser cathodes is based on the impurity mechanism.
  • the purpose of the activation process is to create a sufficient quantity of excess elementary alkaline earth metal via which the oxides in the electron-emitting coating can supply the maximum emission flow at a specified heating capacity.
  • the reduction of barium oxide to elementary barium through alloy components (activators) of metal matrix bodies is an essential contribution to the activation process.
  • U.S. Pat. No. 5,118,317 discloses a method of manufacturing of an impregnated dispenser cathode comprising a porous metal matrix body of a refractory metal serving as an activator, where the porous metal matrix body is formed by compaction of non-interlocking individual powder particles of transition metal coated with a thin layer of a ductile metal and subsequent sintering at a temperature below 600° C.
  • Such a cathode in which the metal matrix body is pressed from a metal powder and sintered has a better emission capacity and longer life as the porous structure of the metal matrix body supports the surface reaction between the activator metal and the actual emission material.
  • the object of the invention is to provide a method of manufacturing a dispenser cathode for a cathode ray tube, the beam current of which is uniform and remains constant over a long time, and which can be reproducibly manufactured.
  • the object is achieved by a method of manufacturing a dispenser cathode for a cathode ray tube which comprises a cathode carrier with a cathode base of a cathode metal and a metal matrix body of a matrix of metal particles of a metal selected from the group of the refractory metals and infiltrated into the matrix, oxide particles of an alkaline earth oxide selected from the group of oxides of calcium, strontium and barium, where the matrix is produced from metal particles of a metal selected from the group of refractory metals by reduction of a porous stabilized oxide gel of the metal selected from the group of refractory metals.
  • Such a dispenser cathode has a uniform beam current over a long period of time as the matrix has an open microstructure due to the method according to the invention.
  • the improved surface properties lead firstly to an already high initial emission and secondly to a low poisoning resistance to oxygen.
  • the open microstructure also increases the Ba retention.
  • the cathode is not susceptible to ion bombardment, has an even emission and can be manufactured reproducibly. Due to the continuous barium supply, exhaustion of the electron emission as occurs in conventional dispenser cathodes is avoided. Substantially higher current beam densities can be achieved without endangering the cathode life. It can also be utilized to draw the necessary electron beam currents flows from smaller cathode areas. The size of the cathode spot is decisive for the quality of beam focusing on the screen. Picture sharpness over the entire screen is increased. As, in addition, the cathodes are not subject to aging, the image brightness and sharpness can be kept stable at a high level over the entire life of the tube.
  • This wet chemical and/or aerosol-based process is more variable, more flexible and economic than the powder metallurgical processes conventionally used. This is due in particular to lower process temperatures below 1000° C. in comparison with the sintering and impregnation process above 1600° C. in the conventional method.
  • the porous stabilized oxide gel of a refractory metal is produced by a reaction of a starting compound of the refractory metal with a microstructure control additive.
  • Preferred microstructure-control additives are a block copolymer R′R′′R′(OH) 2 , an emulsion, a reaction-modifying reagent and a polymer.
  • the metal matrix body is produced with 20 to 80 vol % metal and 20 to 80 vol % oxide.
  • the metal matrix body is produced with 20 to 80 vol % metal and 20 to 80 vol % oxide.
  • the dispenser cathode is characterized by robust behavior on rapid switching.
  • the invention offers particularly advantageous effects in relation to the state of the art if the porous metal matrix body is coated with a cover layer containing a metal selected from the group Ir, Os, Re, Ru and W, by precipitation of the oxides or hydroxides of metals selected from the group Ir, Os, Re, Ru and W on the surface of the porous metal matrix and subsequent reduction to the metal.
  • a metal selected from the group Ir, Os, Re, Ru and W a metal selected from the group Ir, Os, Re, Ru and W
  • the porous metal matrix body can be coated with a cover layer containing a barium-calcium-aluminate.
  • a cathode ray tube comprises an electron beam generating system which usually includes an arrangement with one or more dispenser cathodes.
  • a dispenser cathode according to the invention comprises a cathode carrier with a cathode base and a porous metal matrix body.
  • the cathode carrier contains the heating and the base for the cathode body.
  • the designs and materials known from the state of the art can be used for cathode carriers.
  • the material of the cathode base is usually a nickel alloy.
  • the nickel alloy for the base of the dispenser cathode according to the invention can for example consist of nickel with an alloying proportion of a reducing activator element selected from the group silicon, magnesium, aluminum, tungsten, molybdenum, manganese and carbon.
  • the metal matrix body contains infiltrated oxide particles.
  • the main components of the oxide particles are oxide particles of an alkaline earth oxide, preferably barium oxide, together with calcium oxide and/or strontium oxide.
  • the alkaline earth oxides are used as a physical mixture of alkaline earth oxides or as binary or ternary mixed crystals of the alkaline earth metal oxides.
  • a ternary alkaline earth mixed crystal oxide of barium oxide, strontium oxide and calcium oxide or a binary mixture of barium oxide and calcium oxide is preferred.
  • the alkaline earth oxide can contain a doping of an oxide selected from the oxides of scandium, yttrium and the lanthanoids lanthanum, cerium, praseodymium, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium, e.g. in a quantity of 10 to a maximum 1000 ppm.
  • the metal matrix body also contains a matrix of metal particles of a metal selected from the group of refractory metals Mg, Al, Fe, Si, Ti, Hf, Zr, W, Mo, Mn and Cr.
  • the components of the porous metal matrix are arranged in a particle-particle composite with open pores. Particularly advantageous effects in relation to the state of the art are given by a dispenser cathode according to the invention with a particle-particle composite in which the pore dimensions have a gradient towards the surface. In this dispenser cathode the Ba retention is particularly improved.
  • the microstructure of the metal matrix can also be improved further if the metal particles have a transition from one metal to another in a longitudinal direction.
  • the porous metal matrix can also contain a coating.
  • the porous metal matrix can be covered with a cover layer which contains one of the metals Ir, Os, Re, Ru or W or a combination thereof.
  • This layer can be formed by the precipitation of the corresponding oxides or oxide hydrates on the surface of the metal matrix and subsequent reduction to metals. This gives preferably a cover layer with a thickness of 1 to 30 ⁇ m with pores in the submicron range.
  • the porous metal matrix can also be coated with a cover layer containing oxide particles of an alkaline earth oxide selected from the group of oxides of calcium, strontium and barium and oxide particles of an oxide selected from the group of oxides of scandium, yttrium and the lanthanoids.
  • cover layer with pores in the submicron range a rapid lateral diffusion supply of barium to the surface of the dispenser cathode occurs as the lateral dimensions are smaller than the diffusion lengths. This leads to longer life and low operating temperatures for the dispenser cathode.
  • cover layer is produced by precipitation of the corresponding oxides or oxide hydrates on the surface of the metal matrix and subsequent reduction to the metals, in the cover layer a continuous transition can be achieved from course pores to fine pores in the direction of the emitting surface, which guarantees a good barium supply even under ion bombardment and simultaneously reduces the barium vaporization due to the low operating temperature.
  • the matrix of metal particles of a metal selected from the group of the refractory metals is produced by reduction of an oxide gel of the metal selected from the group of refractory metals.
  • the refractory metals comprise the refractory metals Mg, Al, Fe, Si, Ti, Hf, Zr, W, Mo, Mn and Cr.
  • Chemical starting compounds serve as the start for the metal oxide phase. These can for example be halogenides, carbonyls, alcoholates or metal hydroxides.
  • tungsten for example WCl 6 , W(CO) 6 , W(OC 2 H 5 ) 6 or H 2 WO 4 can be used and for a matrix of nickel NiCl 4 .
  • These compounds are brought into solution, preferably an alcoholic solution.
  • microstructure-control additives can be block copolymers R′R′′R′(OH) 2 , emulsions e.g. oil-water emulsions, reaction-modifying reagents and polymers.
  • the reaction leads to the corresponding oxides and oxide hydrates as gels with controlled microstructure and morphology.
  • the oxide gel is then reacted with a reducing agent for example with 5% in nitrogen-hydrogen at 500 to 1000° C., in order to obtain a porous metal matrix with controlled microstructure and morphology.
  • block polymers R′R′′R′(OH) 2 act as “molecular templates” which cause a pseudo-sol-gel precipitation and stabilize the oxide gels.
  • the pore distribution of the oxide gel with controlled microstructure and porosity is determined for example by the drop characteristics of the original emulsion. Oil and other organic components of the emulsion are then removed by a first temperature treatment at 400 to 600° C. The porous oxide gel is then converted via reduction with a hydrogen-nitrogen mixture at 500 to 1000° C. into a porous metal matrix with controlled microstructure and porosity.
  • a conventional infiltration, a gel or a wet chemical infiltration technique can be used to fill the pores of the metal matrix with barium-calcium-aluminate or another barium-oxide-containing material.
  • the carbonates of the alkaline earth metals calcium, strontium and barium are ground and mixed together and where applicable mixed with a starting compound for the oxide of scandium, yttrium, lanthanum, cerium, praseodymiumn, neodymium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium and lutetium in the required weight ratio.
  • Preferred starting compounds for the oxides of scandium, yttrium and the lanthanoids are the nitrates or hydroxides of these elements.
  • the weight ratio of calcium carbonate: strontium carbonate: barium carbonate is 1:1.25:6 or 1:12:22 or 1:1.5:2.5 or 1:4:6.
  • the carbonates of the alkaline earth metals can be co-precipitated with the nitrates of scandium, yttrium and the lanthanoids.
  • the raw material can also be mixed with a binding agent preparation.
  • the binding agent preparation can contain as a solvent water, ethanol, ethylnitrate, ethylacetate or diethylacetate.
  • the dispenser cathode in an integrated process in which the matrix preparation and oxide infiltration take place in the same step.
  • the differential oxide stabilities of the refractory metals and alkaline earth metals allow formation of the metal phase in situ.
  • the dispenser cathode is integrated into the cathode ray tube. During evacuation of the cathode ray tube the dispenser cathode is formed. By heating to around 650 to 1100° C. the alkaline earth carbonates are converted into alkaline earth oxides while releasing CO and CO 2 and then form a porous sinter compound. The crystallographic change by mixed crystal formation, which is a prerequisite for a good dispenser cathode, is essential in this conversion process. After this cathode “burn-off”, activation takes place with the purpose of supplying excess elementary alkaline earth metal embedded in the oxides. The excess alkaline earth metal is obtained through reduction of alkaline earth metal oxide. In the actual reduction activation, the alkaline earth oxide is reduced by the released CO or activator metal from the cathode base and the metal matrix. Then current activation takes place which generates the necessary free alkali earth metals by electrolytic processes at high temperatures.
  • the production process according to the invention is an efficient method for composite cathode body structures with gradients in material and structure, for example in the form of metal lattice structures e.g. of Ni, porous metal matrices e.g. of tungsten, or metal components which contain activators for barium release. It also comprises the spray deposition of complex-composition dispenser cathode structures with functional gradients in conjunction with molecular self-assembly techniques based on emulsion and foaming methods. Typical examples of structures which can be produced with the process according to the invention are sprayed dispenser cathode layer structures with Ni particle single layers, dispenser cathodes with double layers in the metal matrix, foamed metal matrix structures and porous metal matrix structures with controlled porosity. It is also possible to align elongated Ni particle chains via a magnetic field.

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  • Engineering & Computer Science (AREA)
  • Manufacturing & Machinery (AREA)
  • Solid Thermionic Cathode (AREA)
  • Electrodes For Cathode-Ray Tubes (AREA)
US10/135,338 2001-05-02 2002-04-30 Method of manufacturing a dispenser cathode for a cathode ray tube Abandoned US20020193041A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE10121445.6 2001-05-02
DE10121445A DE10121445A1 (de) 2001-05-02 2001-05-02 Verfahren zur Herstellung einer Vorratskathode für eine Kathodenstrahlröhre

Publications (1)

Publication Number Publication Date
US20020193041A1 true US20020193041A1 (en) 2002-12-19

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US10/135,338 Abandoned US20020193041A1 (en) 2001-05-02 2002-04-30 Method of manufacturing a dispenser cathode for a cathode ray tube

Country Status (4)

Country Link
US (1) US20020193041A1 (de)
EP (1) EP1255274A2 (de)
JP (1) JP2003016931A (de)
DE (1) DE10121445A1 (de)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20080025864A1 (en) * 2006-07-19 2008-01-31 Jinshu Wang Method of manufacturing a pressed scandate dispenser cathode
RU174300U1 (ru) * 2017-06-14 2017-10-11 Демидова Елена Викторовна Торцевой металлопористый катод

Citations (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4675570A (en) * 1984-04-02 1987-06-23 Varian Associates, Inc. Tungsten-iridium impregnated cathode
US4810926A (en) * 1987-07-13 1989-03-07 Syracuse University Impregnated thermionic cathode
US4873052A (en) * 1984-10-05 1989-10-10 U.S. Philips Corporaton Method of manufacturing a scandate dispenser cathode and scandate dispenser cathode manufactured according to the method
US4982133A (en) * 1988-11-11 1991-01-01 Samsung Electron Device Co., Ltd. Dispenser cathode and manufacturing method therefor
US5007874A (en) * 1990-10-15 1991-04-16 The United States Of America As Represented By The Secretary Of The Army Method of making a cathode from tungsten and iridium powders using a reaction product from reacting a group III A metal with barium peroxide as an impregnant
US5112707A (en) * 1983-09-26 1992-05-12 Canon Kabushiki Kaisha Mask structure for lithography
US5114742A (en) * 1991-07-17 1992-05-19 The United States Of America As Represented By The Secretary Of The Army Preparing a scandate cathode by impregnating a porous tungsten billet with Ba3 Al2 O6, coating the top surface with a mixture of Sc6 WO12, Sc2 (WO4)3, and W in a 1:3:2 mole ratio, and heating in a vacuum
US5306189A (en) * 1991-09-18 1994-04-26 Nec Corporation Cathode impregnated by an electron emissive substance comprising (PBAO.QCAO).NBAA1204, where P>1, Q>0, N>1
US5318468A (en) * 1991-05-07 1994-06-07 Licentia Patent-Verwaltungs-Gmbh Dispenser cathode and process for preparing it
US5407633A (en) * 1994-03-15 1995-04-18 U.S. Philips Corporation Method of manufacturing a dispenser cathode
US5417600A (en) * 1992-01-22 1995-05-23 Mitsubishi Denki Kabushiki Kaisha Method of manufacturing an impregnation type cathode
US5507675A (en) * 1993-06-22 1996-04-16 Thorn Microwave Devices Limited Method of manufacturing a thermionic cathode structure
US6425793B1 (en) * 1997-11-04 2002-07-30 Sony Corporation Impregnated cathode and method of manufacturing same, electron gun and electron tube

Patent Citations (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5112707A (en) * 1983-09-26 1992-05-12 Canon Kabushiki Kaisha Mask structure for lithography
US4675570A (en) * 1984-04-02 1987-06-23 Varian Associates, Inc. Tungsten-iridium impregnated cathode
US4873052A (en) * 1984-10-05 1989-10-10 U.S. Philips Corporaton Method of manufacturing a scandate dispenser cathode and scandate dispenser cathode manufactured according to the method
US4810926A (en) * 1987-07-13 1989-03-07 Syracuse University Impregnated thermionic cathode
US4982133A (en) * 1988-11-11 1991-01-01 Samsung Electron Device Co., Ltd. Dispenser cathode and manufacturing method therefor
US5007874A (en) * 1990-10-15 1991-04-16 The United States Of America As Represented By The Secretary Of The Army Method of making a cathode from tungsten and iridium powders using a reaction product from reacting a group III A metal with barium peroxide as an impregnant
US5318468A (en) * 1991-05-07 1994-06-07 Licentia Patent-Verwaltungs-Gmbh Dispenser cathode and process for preparing it
US5114742A (en) * 1991-07-17 1992-05-19 The United States Of America As Represented By The Secretary Of The Army Preparing a scandate cathode by impregnating a porous tungsten billet with Ba3 Al2 O6, coating the top surface with a mixture of Sc6 WO12, Sc2 (WO4)3, and W in a 1:3:2 mole ratio, and heating in a vacuum
US5306189A (en) * 1991-09-18 1994-04-26 Nec Corporation Cathode impregnated by an electron emissive substance comprising (PBAO.QCAO).NBAA1204, where P>1, Q>0, N>1
US5417600A (en) * 1992-01-22 1995-05-23 Mitsubishi Denki Kabushiki Kaisha Method of manufacturing an impregnation type cathode
US5507675A (en) * 1993-06-22 1996-04-16 Thorn Microwave Devices Limited Method of manufacturing a thermionic cathode structure
US5407633A (en) * 1994-03-15 1995-04-18 U.S. Philips Corporation Method of manufacturing a dispenser cathode
US6425793B1 (en) * 1997-11-04 2002-07-30 Sony Corporation Impregnated cathode and method of manufacturing same, electron gun and electron tube

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20080025864A1 (en) * 2006-07-19 2008-01-31 Jinshu Wang Method of manufacturing a pressed scandate dispenser cathode
US7722804B2 (en) * 2006-07-19 2010-05-25 Beijing University Of Technology Method of manufacturing a pressed scandate dispenser cathode
RU174300U1 (ru) * 2017-06-14 2017-10-11 Демидова Елена Викторовна Торцевой металлопористый катод

Also Published As

Publication number Publication date
JP2003016931A (ja) 2003-01-17
EP1255274A2 (de) 2002-11-06
DE10121445A1 (de) 2002-11-07

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Owner name: KONINKLIJKE PHILIPS ELECTRONICS N.V., NETHERLANDS

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNORS:GAERTNER, GEORG FRIEDRICH;GOODHAND, CHRISTOPHER JAMES;HODGSON, SIMON NICHOLAS;AND OTHERS;REEL/FRAME:013174/0983;SIGNING DATES FROM 20020514 TO 20020612

STCB Information on status: application discontinuation

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